Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$68.33	5.369%	$71.9986	$72.00	$72.00	$72.00
Purchase #2	$50.85	6.594%	$54.203	$54.20	$54.20	$54.20
Purchase #3	$89.65	3.128%	$92.4543	$92.45	$92.45	$92.50
Purchase #4	$156.30	5.300%	$164.5839	$164.58	$164.60	$164.60
Purchase #5	$81.93	10.396%	$90.4474	$90.45	$90.45	$90.40
Purchase #6	$158.42	6.696%	$169.0278	$169.03	$169.05	$169.00
Purchase #7	$54.46	13.614%	$61.8742	$61.87	$61.85	$61.90
7 purchase totals =	$659.94		$704.5892	$704.58	$704.60	$704.60